Self-propelled earth working machine having a coolant discharge tank

The present application claims priority to German patent application Ser. No. DE 10 2022 119 272.5 filed Aug. 1, 2022, which is incorporated herein by reference.

The present invention relates to a self-propelled earth working machine, which comprises:

Such an earth working machine is known very generally from EP 3 901 373 A1 (U.S. Pat. No. 11,401,665) for example. This known earth working machine, the features of which may also be realized in the earth working machine of the present invention, supports a cutting drum as a working apparatus, which is used for texturing ground surfaces. The cutting drum, also called a grinding drum or grooving drum, is rotatable about a working axis running in parallel to the transverse machine direction. It comprises one or multiple cutting disks revolving about the working axis configured with geometrically defined cutters and/or with geometrically undefined cutters, for example in the form of cutting grains bonded to the cutting disks. Cutting drums of this kind may be used for example to cut grooves into a ground surface. The rotation of the cutting drum about the working axis produces the required cutting speed on the cutters situated on the cutting drum. The forward motion is produced by the travel drive via the traveling gear of the earth working machine.

A road milling machine as a further earth working machine is known from EP 3 613 900 A1 (U.S. Pat. No. 10,711,414). The known road milling machine also comprises a working apparatus rotatable about a working axis running in the transverse machine direction. The working apparatus of the road milling machine is a milling drum equipped with individual milling bits. In contrast to the cutting drum having continuously or quasi-continuously revolving cutting disks configured with cutters, the milling bits with their earth-removing bit tips are arranged in a spiral-shaped manner on the outer surface of the milling drum so as to improve the transport of the milled material produced by the earth removal. Normally, only one milling bit is situated at an axial position of the working axis of a milling drum. In road milling machines, the rotation of the milling drum about the working axis also produces the required cutting speed of the milling bit tips, while the forward motion of the milling drum is produced by the travel drive of the road milling machine.

For reasons of occupational safety and health, the working apparatus is enclosed on the working unit so that at least during an earth working operation it is not accessible from outside. The working unit may therefore comprise a housing as a housing enclosure which is open toward the ground to be worked. Such a housing is known as a milling drum box in road milling machines. A box functionally equivalent to the milling drum box, which shields a cutting drum on both sides in the transverse machine direction, on both sides in the longitudinal machine direction and in the vertical machine direction toward the machine frame, may be provided on the working unit of a ground-texturing machine.

The working unit may comprise further functional modules such as transmissions transmitting movement and power, heat exchangers, and the like.

In their normal operation, both of the mentioned types of earth-removing working apparatuses are cooled by liquid coolant, which is conducted by the liquid cooling apparatus into the working unit, in particular into the housing enclosure of the working apparatus. Normally, the liquid coolant is sprayed onto the working apparatus and/or into the area where the working apparatus engages with the earth to be removed. The liquid coolant is normally water, which is carried by the earth working machine in a reservoir.

Due to the different situation at the working engagement described above, the cutting working apparatus has a considerably higher cooling requirement than the milling working apparatus. At a lower cooling requirement, the quantity of liquid coolant fed into the working unit does not present a problem. In a milling earth removal operation at a low cutting speed, the liquid coolant at most moistens the surroundings of the working apparatus and is discharged from the working unit along with the removed coarse-grained chips. A further portion of the liquid coolant remains as moisture in the worked ground.

With an increasing cooling requirement, beginning at a specific operating point, more liquid coolant is introduced per unit of time into the working unit than can seep away in the worked ground and discharged with the removed chips. This state is amplified by two further effects:

On the one hand, the increasing cooling requirement is associated with an increasing cutting speed and consequently a greater reduction in the size of the chips produced in the earth working operation. While in a milling operation at a comparatively low cutting speed, clod-like or coarse-grained chips are quarried out of the ground surface, which can be handled as coarse bulk material, with increasing cutting speed, in particular the in transition to a cutting operation, the removed chips increasingly assume a finely grained, mealy structure and start to silt up the liquid coolant when coming into contact with it.

On the other hand, with increasing cutting speeds, not only does the volume of the individual removed chips decrease, but the removed volume or chip volume per unit of time as a whole decreases. While road milling machines are designed to remove earth material substantially in order to produce a remaining residual ground layer as a foundation for a new ground buildup, the cutting drums are merely to texture the ground surface, for example by cutting in grooves. Hence, with an increasing cooling requirement, the ability of the presently worked ground to absorb moisture or liquid often decreases.

For this reason, it is standard practice in the prior art to remove the liquid coolant actively from the earth working zone upon exceeding the aforementioned operating point with the critical cooling requirement. Due to the great quantities of liquid, used liquid coolant is transferred to a discharge vehicle, which is connected to the earth working machine by a hose line in a fluid-conducting manner. The discharge vehicle travels next to the earth working machine during the earth working operation, while used liquid coolant is transferred from the earth working machine to the discharge vehicle.

A disadvantage of this approach is on the one hand that in the event of a high cooling requirement the availability of the earth working machine depends on the availability of the discharge vehicle and that on the other hand the joint operation of the earth working machine and the discharge vehicle triggers an additional coordination requirement, for example in order to prevent the line connection established between the discharge vehicle and the earth working machine from being severed.

It is therefore an object of the present invention to increase the availability of the earth working machine even in the event of a high cooling requirement at the point of engagement for the earth working operation and to avoid sources of error in the earth working operation.

The present invention achieves this object on a self-propelled earth working machine mentioned at the outset in that the earth working machine comprises a discharge tank and a discharge line system, the discharge line system connecting the working unit to the discharge tank in fluid-conducting fashion and being designed to conduct liquid coolant from the working unit into the discharge tank.

The discharge tank removes the direct dependence of the earth working machine on the availability of a discharge vehicle in operating situations with a high cooling requirement. The length of time, over which the earth working machine is able to operate with a high cooling requirement, depends on the holding capacity of the discharge tank. The discharge tank preferably has a holding capacity of at least 1,000 l (liters), particularly preferably of at least 2,000 l. Even more preferably, the holding capacity of the discharge tank is greater than 2,100 l. For reasons of stability of the machine frame and in consideration of the total weight of the earth working machine, the holding capacity of the discharge tank is preferably less than 5,000 l, particularly preferably less than 4,000 l and more preferably less than 3,000 l. In a currently constructed version, the holding capacity of the discharge tank is less than 2,500 l. The precise holding capacity for liquid coolant, however, depends not only on the outer dimensions of the discharge tank, but also on its inner structure.

The discharge line system allows for a very advantageous free choice of the location at which to mount the discharge tank on the earth working machine. This advantageously makes it possible to situate the discharge tank on the earth working machine at a distance from the working unit, so that it is possible not only to equip new earth working machines with a discharge tank, but also to retrofit existing earth working machines with a discharge tank.

The working apparatus may be or comprise a cutting drum described at the outset for texturing ground surfaces, in particular for introducing grooves into the ground surface. Additionally or alternatively, the working apparatus may be or comprise a milling drum described at the outset. What was said above about the known earth working machine equipped with a cutting drum and about the known road milling machine applies to the cutting drum or milling drum and the earth working machine of the present invention equipped with these.

As in the prior art, the liquid coolant for the earth working machine of the present invention is preferably water.

In principle, it is conceivable to situate a discharge transfer pump in the discharge line system in order to provide the necessary pressure drop in the discharge line system for the controlled conveyance of liquid coolant from the working unit to the discharge tank. According to a preferred development of the present invention, the discharge tank additionally or preferably alternatively has a vacuum apparatus, which is designed to remove gas from the discharge tank. This vacuum apparatus can be used to generate an underpressure, which provides the pressure drop required for transferring liquid coolant from the working unit to the discharge tank. The gas is normally air. It shall not be precluded, however, that an atmosphere different than air is produced in the gas-filled space above the liquid coolant in the discharge tank, for example in order to impede the growth of aerobic microbes.

The vacuum apparatus is preferably designed to produce a pressure in the gas-filled space in the interior of the discharge tank that is at least 18 hPa lower than the ambient pressure outside of the discharge tank, preferably at least 22 hPa lower, even more preferably at least 24 hPa lower. An underpressure in the discharge tank compared to the ambient pressure with a pressure difference of −40 hPa should suffice in preferred specific embodiments to transfer even large quantities of liquid coolant per unit of time over long line paths from the working unit to the discharge tank. A pressure difference compared to the ambient pressure of −34 hPa is reliably able to transfer slightly above-average quantities of liquid coolant per unit of time. With a view to avoiding unnecessary investments in vacuum apparatuses, the price of which increases with their maximally possible vacuum power, an underpressure compared to the ambient pressure with a pressure difference of −27 hPa may suffice for most earth working applications. The vacuum apparatus is therefore preferably designed in such a way that it produces a pressure in the discharge tank that is lower than the ambient pressure by no more than 40 hPa, particularly preferably by no more than 34 hPa, even more preferably by no more than 27 hPa.

The vacuum apparatus may comprise at least one ventilator, preferably a plurality of ventilators, in order to remove gas, in particular air, from the discharge tank. Preferably, a ventilator system having one or multiple ventilators is situated on a—when looking at the operational earth working machine—top side of the discharge tank, so that during an earth working operation it is reached as late as possible or preferably not reached at all by the liquid coolant level rising in the discharge tank. The top side of the discharge tank is therefore preferably formed by a plane wall or by a wall that is convex when looking at the top side of the discharge tank from outside and thus concave when looking at the top side of the discharge tank from inside, the plane or curved wall supporting the vacuum apparatus, in particular its ventilator system.

In order to achieve a sufficient relative underpressure in the discharge tank compared to the ambient atmosphere, the ventilator system as a whole may have a conveying capacity during earth working operation of at least 10,000 m/h at a standard air atmosphere of 20° C. and 1013 h Pa. More preferably, the conveying capacity of the ventilator system during earth working operation is at least 13,000 m/h, even more preferably at least 16,000 m/h, respectively at the mentioned standard air atmosphere as test atmosphere.

In order to avoid excessive energy consumption and excessive installation space requirement, the ventilator system is preferably designed for a conveying capacity during earth working operation of no more than 30,000 m/h at the standard air atmosphere. More preferably, the conveying capacity of the ventilator system during earth working operation is no more than 24,000 m/h, even more preferably no more than 19,000 m/h, respectively at the mentioned standard air atmosphere as test atmosphere. The ventilator system is preferably designed in accordance with the upper performance requirements. For example, the ventilator system may have corresponding nominal conveying capacities.

In the preferred case, where the ventilator system comprises a plurality of ventilators, the nominal conveying capacities of air conveyed per hour at standard air atmosphere differ by no more than 15%, preferably by no more than 10%, relative to the greater of two compared nominal conveying capacities. Particularly preferably, the ventilators of a ventilator system are designed with the same nominal conveying capacity. Most preferably, only identical ventilators are combined to form a ventilator system of the vacuum apparatus.

As was already described above, the presently discussed operating case with a high cooling requirement occurs at high cutting speeds and low chip volume, which increases the tendency of the used liquid coolant to silt with fine-grained chip material suspended in the liquid coolant. In order to prevent chip material suspended in the liquid coolant from settling in the discharge tank, the discharge tank may comprise a motion apparatus, which is designed to set and/or keep liquid coolant collected in the discharge tank in motion. The motion apparatus may be a splash device, which in reciprocating fashion moves a splash blade back and forth in the interior volume of the discharge tank. The motion apparatus is preferably a stirring apparatus, which by a rotating motion of a stirring tool is designed to stir liquid coolant collected in the discharge tank. The movement space of a stirring tool is smaller than that of a splash blade, and at an identical quantity of liquid in the discharge tank, eddies in the discharge tank often require the absorption of lesser bearing forces than splash motions.

In principle, it is conceivable to design the discharge tank using a vat and a removable cover covering the vat. The vat preferably surrounds the major part of the receiving volume of the tank. The cover preferably supports the vacuum apparatus and comprises the aforementioned plane or curved upper tank wall. When the nominal filling capacity of the discharge tank is reached, it is in principle conceivable to detach the full vat from the cover and, if indicated, from the machine frame and to exchange it for an empty vat. However, this requires further machine use on the construction site.

For discharging the discharge tank, the earth working machine may have a transfer pump, which is designed to transfer liquid coolant collected in the discharge tank from the discharge tank. The transfer pump can then transfer the liquid coolant from the discharge tank into a further tank, which may be mounted on a trailer for example and may be towed by the earth working machine as the towing vehicle or which may be pushed by the earth working machine. The transfer pump may also transfer liquid coolant from the discharge tank into a tank of a discharge vehicle, with which the operating personnel at the construction sites is already familiar. The advantage still persists that the discharge vehicle is required only temporarily and that its use may be scheduled and shifted within certain temporal limits without loss of the availability of the earth working machine.

For the conveyance of liquid, the transfer pump is preferably designed with a conveying capacity that allows for a conveyance per hour of more than the holding capacity of the discharge tank. The conveying capacity of the transfer pump preferably is at least 3,200 l/h, particularly preferably at least 3,500 l/h and even more preferably at least 3,800 l/h. For reasons of economy with a view to a maximally possible holding capacity of the discharge tank, the conveyance capacity of the transfer pump is preferably no more than 6,000 l/h, more preferably no more than 5,000 l/h and even more preferably no more than 4,200 l/h.

In order to clean the used and therefore soiled liquid coolant and thus to facilitate its further processing or disposal, the earth working machine may comprise a filter apparatus, which is designed to filter particles, in particular chip material of the removing earth working operation, which are suspended in the liquid coolant collected in the discharge tank, out of the liquid coolant. This makes it possible to reduce the portion of particles suspended in the liquid coolant considerably.

So as not to impede a discharge of the liquid coolant from the working unit, it is preferred to situate the filter apparatus in the conveyance line of the transfer pump so that liquid coolant flows through the filter apparatus when, in particular only when, the transfer pump is in operation in order to transfer liquid coolant out of the discharge tank. The filter apparatus may be accommodated in the discharge tank, which is less preferable, however, due to the associated loss of storage volume for receiving liquid coolant and the associated effort for exchanging or cleaning filter elements. The filter apparatus may be accommodated on the outer side of the discharge tank to ensure that together with the discharge tank, the filter apparatus is also always carried along with the earth working machine. As a further alternative, the filter apparatus may be situated on a supporting frame firmly connected to the discharge tank, but at a distance from the tank wall so as to provide the filter apparatus in a manner that is accessible from as many sides as possible. The filter apparatus may also be accommodated on the machine frame at a distance from the discharge tank.

The earth working machine usually has a reservoir in order to provide liquid coolant for use to the liquid cooling apparatus. This reservoir preferably has a holding capacity of at least 2,900 l, more preferably of at least 3,200 l and even more preferably of at least 3,400 l. Considering the cooling requirement on the one hand and the total weight of the earth working machine, the holding capacity of the reservoir is preferably not greater than 6,000 l, particularly preferably not greater than 4,500 l and even more preferably not greater than 3,700 l. Further preferably, the holding capacity of the reservoir is greater than the holding capacity of the discharge tank, so that starting from an onset of the operation with a completely filled reservoir and a completely emptied discharge tank, the discharge tank forms the operation-limiting component with regard to the required cooling. Ultimately, it is easier to empty a full tank than to have to fill an empty tank.

Freed of the requirement of a discharge vehicle, the operating time of the earth working machine can be extended further in that a return line connects the discharge tank to the reservoir by interposition of the filter apparatus and the transfer pump. This makes it possible for the transfer pump to transfer filtered liquid coolant, that is, preferably water, from the discharge tank back into the reservoir, from where the liquid coolant can be fed again to the working unit. The filter apparatus may be situated on the suction side or on the pump side or as a split filter apparatus on both sides of the transfer pump. Preferably, the filter apparatus is situated on the suction side of the transfer pump so that liquid coolant flowing through the transfer pump has already been cleaned and thus in operation puts less abrasive stress on the transfer pump.

To avoid damage and excessive noise generation when soiled liquid coolant rushes into the discharge tank, according to a preferred development, a baffle is situated in the discharge tank downstream from an inlet of the discharge line system into the discharge tank and preferably at a distance from the inlet. The baffle may be a rigid body such as a plate or a shield made of metal or ceramic, for example. In a preferred specific embodiment, the baffle may comprise elastic, for example elastomeric, planar bodies such as a plate or a lip made of, preferably reinforced, rubber or silicone rubber or another elastomer, for example. When liquid coolant is transferred through the discharge line system into the discharge tank, the liquid coolant emerging from the discharge line system strikes the baffle.

The inlet of the discharge line system into the discharge tank is preferably in the upper half of the discharge tank, when looking at it in the operational state, particularly preferably in the upper quarter of the discharge tank, so that the vacuum apparatus is able to transfer liquid coolant from the working unit into the discharge tank over the longest possible operating time without the counteraction of a back pressure from a liquid volume rising in the discharge tank.

The earth working machine may comprise a connection formation in fluid communication with the discharge tank for temporary connection of a fluid line, for example for connecting a fluid line leading to a discharge vehicle. This makes it possible to withdraw liquid coolant from the discharge tank, preferably while the latter is situated on the earth working machine and particularly preferably during an earth working operation, in order to increase again the storage capacity of the discharge tank in the respective situation.

The connection formation may be formed directly in the tank wall or permanently connected to the tank wall as a connection fitting or at the longitudinal end, remote from the tank, of a flexible line connected to the discharge tank, which makes it possible to eliminate the need for lines between the discharge tank and the connection formation or at least to keep these short. In addition, for example if the transfer pump is accommodated in the interior of the discharge tank, or alternatively, the connection formation may be situated or formed on the transfer pump or on a longitudinal end, remote from the pump, of a pressure-side transfer line of the transfer pump. It is thus possible to provide the connection formation at nearly any location on the earth working machine. In addition, on the side of the earth working machine, the transfer pump is always able to transfer liquid coolant out of the discharge tank, regardless of the structure or equipment of the transfer target of the transfer pump. The connection formation may be connected to the discharge tank by interposition preferably of the aforementioned filter system.

The transfer pump and/or the filter system and/or the connection formation may be accommodated on the aforementioned supporting frame connected to the tank wall.

The presently discussed earth working machine may be any self-propelled earth working machine having a cooling requirement. Preferably, as explained in detail above, the machine is an earth-removing earth working machine. The working apparatus is then preferably a removal apparatus rotatable about a working axis such as the cutting drum or milling drum described above. The working axis normally runs in the transverse machine direction, that is, in parallel to the pitch axis of the self-propelled earth working machine.

The earth working machine is preferably retoolable between for example a working unit having a first earth working function and a further working unit having a second earth working function distinct from the first. A working unit may be for example a cutting unit having a cutting drum for texturing cutting work on a ground surface as a first earth working function. A further working unit may be for example a milling unit having a milling drum for removing entire earth layers from the ground surface as a second earth working function.

Additionally or alternatively, the earth working machine may be retoolable between a working unit requiring maintenance and an operationally ready working unit, each having the same earth working function.

The working unit is therefore preferably a swappable working unit designed to be detachable from the machine frame. As a swappable working unit, the working unit thus preferably has coupling formations for coupling with mating coupling formations on the machine frame. A coupling formation on the swappable unit and a mating coupling formation on the machine frame cooperating with the coupling formation may be in each case a fastening lug having mutually facing lug surfaces, which are designed to abut against each other. The lug surfaces are preferably plane lug surfaces. For fixing the fastening lugs to each other, at least one of the fastening lugs has a through hole. The other fastening lug may then have a fastening projection penetrating through the through hole when an abutting engagement of the lug surfaces is established. The fastening projection may comprise a threaded rod designed to clamp the fastening lug having the through hole between the fastening lug bearing the fastening projection and a fastening nut that is screwed onto the threaded rod. Alternatively, each of the two fastening lugs may have a through hole, which align with each other when an abutting engagement of the lug surfaces is established, so that the aligned through holes may be connected to each other by a fastening screw and a fastening nut or by a set screw having a fastening nut on each side of the fastening lugs.

Alternatively, the aforementioned fastening projection may be movable hydraulically or pneumatically between a locked position engaging behind the fastening lug having the through hole and a release position disengaging the fastening lug having the through hole for separation from the fasting lug having the fastening projection.

A, possibly additional, coupling formation may comprise a centering body, and a mating coupling formation cooperating with the coupling formation may comprise a centering recess, for example a centering cone or a centering spherical cup as a centering body and a negative-conical centering recess. Such centering coupling formations and mating coupling formations make it possible to ensure quickly and securely that the machine frame and the swappable working unit are in a predetermined relative position and orientation to each other immediately prior to fixing the swappable working unit on the machine frame.

If the machine frame of the presently discussed earth working machine is designed for accommodating a working unit having a milling drum, the machine frame preferably comprises a conveyor belt holding fixture for releasably accommodating a conveyor belt for transporting removed earth material away from the location of the working unit. This applies to an earth working machine that is designed permanently as a road milling machine. This applies in particular, however, to an earth working machine that, owing to coupling interfaces on the machine frame, can be equipped alternatively with a milling unit or with a cutting unit. Although the cutting unit normally does not require a conveyor belt with the transport capacity of a conveyor belt for a road milling machine, the conveyor belt holding fixture is nevertheless extremely advantageous in the event that the earth working machine is tooled as a road milling machine.

Due to the releasable arrangement of the conveyor belt on the machine frame, the discharge tank may be releasably situated on the conveyor belt holding fixture in the event that the earth working machine is retooled for an earth working operation with a high cooling requirement, for texturing cutting work for example.

In the present application, the term “releasable” means intended to be releasable, i.e., the respective component, in this case the conveyor belt and the discharge tank, can be quickly detached from and reattached to the rest of the earth working machine by fastening means intended to be releasable in non-destructive and isolated fashion and without prior disassembly of further components of the earth working machine.

As a road milling machine, the earth working machine is preferably a front loader road milling machine, which transports milled material in the travel direction to or beyond the longitudinal front end of the earth working machine in order to discharge for example milled material into a transport vehicle traveling ahead of the earth working machine. Such front loader road milling machines are designed for high removal volumes per unit of time and accordingly have a sturdy conveyor belt holding fixture. The conveyor belt holding fixture may comprise for example at least one bolt running in the vertical machine direction or preferably at least two bolts arranged coaxially in the vertical machine direction, on which it is possible to fasten not only the conveyor belt, but also the discharge tank. In order to make the at least one bolt easier to reach, the at least one bolt may be situated on a retaining bracket rigidly connected to the machine frame and protruding from the machine frame in the longitudinal machine direction. When using more than one bolt, each bolt is preferably situated on one such retaining bracket.

To facilitate fastening the discharge tank on the machine frame, the earth working machine comprises a support bracket formed separately of the machine frame, which can be hinged on the conveyor belt holding fixture, for example by sliding at least one fastening eye or fastening bushing onto the at least one bolt of the conveyor belt holding fixture. Since the conveyor belt holding fixture preferably has at least two, particularly preferably exactly two coaxially arranged bolts, which respectively project in the same vertical machine direction from the retaining bracket that supports them, the support bracket preferably also has at least two, particularly preferably exactly two, coaxially arranged fastening eyes or fastening bushings in order to be able to brace a turning moment about a turning axis that is parallel to the vertical machine direction on the machine frame.

In a kinematic reversal, the at least one bolt may be situated on at least one retaining bracket of the support bracket and the at least one fastening eye or fastening bushing may be situated rigidly on the machine frame. A bolt projecting on a retaining bracket of the support bracket projects from its retaining bracket in the opposite direction as a bolt fixed on the machine frame so as to ensure that it can be hinged on the fastening eye or fastening bushing.